Scientists have determined that the famous ‘Chicago rat hole,’ a viral sidewalk imprint, was likely made by a squirrel rather than a rat, according to new peer-reviewed research published on October 16, 2025. This finding resolves a long-standing urban mystery that captivated the public and highlights the application of scientific methods to everyday curiosities.
The Chicago rat hole first gained widespread attention in January 2024 when local artist Winslow Dumaine shared a photo on social media, sparking a viral sensation. Located in the Roscoe Village neighborhood, the clear imprint of a rodent’s body in concrete had been a local fixture for decades but quickly became an unlikely tourist attraction. Visitors flocked to the site, leaving offerings like coins and candles, and even holding weddings nearby, turning it into a symbol of Chicago’s gritty charm. Due to neighborhood complaints, the city removed the sidewalk slab in April 2024, though the question of what animal created the imprint remained unanswered.
A team of researchers led by Dr. Michael Granatosky from the University of Tennessee, Knoxville, undertook a scientific investigation to identify the culprit. Using methods akin to paleontology, they analyzed publicly available photographs of the imprint, taking precise measurements of features such as head width, limb lengths, and tail impression. They compared these data to anatomical measurements from museum specimens of eight potential species, including brown rats, house mice, eastern gray squirrels, and fox squirrels, employing statistical models to narrow down the possibilities.
The study, published in the journal Biology Letters, concluded with high probability that the imprint was made by a squirrel, specifically an eastern gray squirrel or a fox squirrel. Key evidence included the elongated forelimbs and hind paws, characteristic of arboreal animals like squirrels, and the absence of features matching brown rats. The researchers estimated a 98.67% likelihood that it was a squirrel and a 50.67% chance it was an eastern gray squirrel, based on the imprint’s dimensions and commonality of species in the area.
Dr. Seth Magle of the Lincoln Park Zoo’s Urban Wildlife Institute, who reviewed the study, expressed vindication, as he had previously speculated based on ecological reasoning that a squirrel was responsible. He noted that squirrels are diurnal and often fall from trees, which aligns with the imprint’s appearance of an animal dropping into wet concrete without drag marks. The scientific community has praised the research for its rigor and ability to engage the public, demonstrating how science can address popular mysteries in an accessible way.
Despite the findings, the rat hole’s cultural significance endures, with many Chicagoans likely to continue using the original name due to its entrenched place in local lore. The concrete slab is currently stored at City Hall, awaiting a permanent public display, as officials recognize its role in community identity. This episode underscores how urban legends can foster a sense of belonging and whimsy, even when scientific evidence challenges initial assumptions.
The investigation also highlights the broader importance of urban ecology, illustrating how wildlife interactions in cities provide opportunities for public education and scientific inquiry. By applying forensic techniques to a modern imprint, researchers bridged the gap between academic science and everyday life, encouraging appreciation for the animals that coexist in urban environments. This approach can inspire future studies on urban wildlife and their impacts on human communities.
In conclusion, the resolution of the Chicago rat hole mystery not only answers a persistent question but also showcases the fun and relevance of scientific exploration. While the imprint may have been made by a squirrel, its legacy as a rat hole reflects the enduring power of storytelling and the value of curiosity-driven research in connecting science with society.